Integrated smoke cell

ABSTRACT

A method includes forming a housing having a ceiling portion and a smoke permeable wall portion. The ceiling portion of the housing has a first aperture and a second aperture. The method includes mounting a circuit board to the housing so that the housing and the circuit board collectively define a smoke chamber that is bounded by the ceiling portion, the smoke permeable wall portion and the circuit board. The method includes placing an emitter in the first aperture and placing a detector in the second aperture. The emitter defines an emitting region in the smoke chamber and the detector defines a detecting region in the smoke chamber. In a typical implementation, the detecting region at least partially intersects the emitting region in the smoke chamber, and the emitter and the detector are disposed substantially outside the smoke chamber.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional application of, and claims priority to,U.S. application Ser. No. 13/717,849 entitled Integrated Smoke Cell,which was filed on Dec. 18, 2012, the disclosure of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to semiconductor devices and moreparticularly, is related to a circuit board mounted smoke sensor.

BACKGROUND OF THE INVENTION

Smoke sensors generally sense the presence of smoke within a chamberbetween an emitter and a detector. FIG. 1A is a schematic diagram of afirst prior art smoke detector 100. Smoke particles enter an opticalchamber 130. The chamber is mounted on a case molding 137, and coveredby a cover 135. The smoke enters the optical chamber through a series ofbaffles 170. The baffles are shaped to allow ingress of smoke into theoptical chamber, but to block direct ingress of light from nearby lightsources. Smoke particles in the path of an emitter 120 are illuminatedby light produced by the emitter 120, and the illuminated smokeparticles scatter the light which is then detected by the detector 110.The emitter 120 and detector 110 are located inside the optical chamber.FIG. 1B is a simplified diagram of the prior art smoke detector, showingan angle α between the orientation of the detector 110 and the emitter120. The emitter 120 and detector 110 are oriented at the angle α toprevent light emitted from the emitter 120 from projecting directly intothe detector 110. The angle α is typically on the order of 135 degrees.Therefore, the detector 110 will only detect light from the emitter 120when the emitted light is scattered in a diffuse manner by discretesmoke particles within the chamber 130. However, since the emitter 120and detector 110 are physically located within the chamber 130, as shownby FIG. 1C, they may block the ingress of smoke entering the chamber 130from some directions, thereby increasing the detection time.

It should be noted that many constraints are placed on the designs ofsmoke cells by regionally specific manufacturing and/or usage standardsdocuments, for example, Deutsche Norm Din En 14604.

FIG. 2 shows a second prior art smoke cell 200, where a smoke chamber230 is formed by a housing having series of baffles 270 and a ceiling260, mounted directly to a printed circuit board (PCB) 250. An emitter220 and a detector 210 are mounted to an optic block 240, where theoptic block 240 is mounted to the PCB 250, inside the smoke chamber 230.The optic block 240 is configured so the angle between the emitter 220and the detector 210 may be on the order of 135 degrees. However, thelocation of the optic block 240 within the smoke chamber 230 mayphysically block smoke from entering the smoke chamber 230.

Therefore, there is a need in the industry to address the shortcomingsdescribed above.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide an integrated smoke celland a method for manufacturing an integrated smoke cell. Brieflydescribed, the present invention is directed to an integrated smoke cellhaving an integral housing including a ceiling portion and a smokepermeable wall portion, the housing substantially defining a chamberwithin the housing. An emitter is mounted substantially above a firstaperture in the ceiling, the emitter having an emitting region adjacentto the emitter disposed within the chamber. A detector is mountedsubstantially above a second aperture in the ceiling, the detectorhaving a detecting region adjacent to the detector disposed within thechamber and at least partially intersecting the emitting region. Theemitter and detector are disposed substantially outside the chamber.

A second aspect of the present invention is directed to a smoke cellconfigured to be mounted on a circuit board including an integralhousing having a ceiling portion and a wall portion. The housingsubstantially defines a chamber within the housing. The wall has aplurality of spaced baffles disposed adjacent to the ceiling, a firstemitter mounted substantially above a first emitter aperture in theceiling, a second emitter mounted substantially above a second emitteraperture in the ceiling, and a first detector mounted substantiallyabove a first detector aperture in the ceiling. The first emitter, thesecond emitter and the first detector are disposed substantially outsidethe chamber.

Briefly described, in architecture, a third aspect of the presentinvention is directed to an integrated smoke cell housing. Theintegrated smoke cell housing includes a ceiling portion having a firstcomponent mount disposed on a first ceiling side substantially above afirst aperture in the ceiling, and a second component mount disposed onthe first ceiling side substantially above a second aperture in theceiling, and a smoke permeable wall portion having a series of spacedbaffles mounted substantially around a perimeter of a second side of theceiling. The first and second component mount are configured to receiveand position a first component and a second component.

A fourth aspect of the present invention is directed to a method formanufacturing an integrated smoke cell having the step of forming anintegral housing having a ceiling portion having a first component mountdisposed on an exterior ceiling side substantially above a firstaperture in the ceiling, and a second component mount disposed on theexterior ceiling side substantially above a second aperture in theceiling and a smoke permeable wall portion having a series of spacedbaffles mounted substantially around a perimeter of an interior side ofthe ceiling. The first component mount is configured to receive andposition a first component and the second component mount is configuredto receive and position a second component.

A fifth aspect includes a method that includes forming a housing havinga ceiling portion and a smoke permeable wall portion. The ceilingportion of the housing has a first aperture and a second aperture. Themethod includes mounting a circuit board to the housing so that thehousing and the circuit board collectively define a smoke chamber thatis bounded by the ceiling portion, the smoke permeable wall portion andthe circuit board. The method includes placing an emitter in the firstaperture and placing a detector in the second aperture. The emitterdefines an emitting region in the smoke chamber and the detector definesa detecting region in the smoke chamber. In a typical implementation,the detecting region at least partially intersects the emitting regionin the smoke chamber, and the emitter and the detector are disposedsubstantially outside the smoke chamber.

Other systems, methods and features of the present invention will be orbecome apparent to one having ordinary skill in the art upon examiningthe following drawings and detailed description. It is intended that allsuch additional systems, methods, and features be included in thisdescription, be within the scope of the present invention and protectedby the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprincipals of the invention.

FIG. 1A is a schematic diagram of a top view a first prior art smokedetector.

FIG. 1B is a simplified schematic diagram of the top view the firstprior art smoke detector.

FIG. 1C is a simplified schematic diagram of a side view the first priorart smoke detector.

FIG. 2 is a schematic diagram of a second prior art smoke cell.

FIG. 3 is a perspective view of the top side of an exemplary firstembodiment of the integrated smoke cell.

FIG. 4 is a perspective view of the underside of the exemplary firstembodiment of the integrated smoke cell.

FIG. 5 is a cutaway perspective view of the exemplary first embodimentof the integrated smoke cell.

FIG. 6 is a schematic diagram of a sectional side view of the interiorof the exemplary first embodiment of the integrated smoke cell detailingthe interference zone.

FIG. 7 is a schematic diagram side view of the interior of the exemplaryfirst embodiment of the integrated smoke cell detailing the relativeangle between the emitter and the detector.

FIG. 8 is a perspective view of the top side of an exemplary secondembodiment of the integrated smoke cell.

FIG. 9 is a flowchart of an exemplary method for manufacturing anintegrated smoke cell.

FIG. 10 is a schematic diagram of a smoke detector system incorporatingthe integrated smoke cell of the current invention.

FIG. 11 is a schematic diagram of the integrated smoke cell in FIG. 6attached to a circuit board.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

As mentioned previously, the presence of emitting and sensing componentswithin a smoke chamber in prior art smoke cells may at least partiallyblock ingress of smoke into the smoke chamber. An object of the currentinvention is a smoke cell having emitters and detectors physicallylocated outside the smoke chamber. A second object for the currentinvention is a smoke cell having all components mounted on the same sideof a PCB. A third object of the current invention is a one piece smokechamber housing that may be formed by injection molding. A fourth objectof the current invention is a smoke cell configured to detect differenttypes of smoke particles without obstructing smoke ingress into thesmoke chamber.

First Embodiment

FIG. 3 shows a first exemplary embodiment of an integrated smoke cell400 under the present invention. The integrated smoke cell 400 includesan integral housing 490 including a ceiling 460 and a side wall formedof a series of baffles 470. A smoke chamber 430 is formed within thehousing 490, bounded by the ceiling 460 and side wall, and furtherbounded by a PCB (not shown) forming a floor of the smoke chamber 430.Under the first embodiment, the side wall formed of a series of baffles470 is substantially circular in shape. However, there is no objectionto a side wall having other shapes, for example, a substantially squareshape, as long as the ability of smoke to enter the chamber 430 issubstantially the same from all directions around the perimeter of theside wall.

The side wall is formed by the series of baffles 470. Each baffle 470 isshaped to be aligned with an adjacent baffle 470 such that a vent isformed between each adjacent baffle 470 allowing smoke to enter thechamber 430 through the vent. The baffles 470 are arranged such that adirect beam of light cannot enter the chamber 430 through the vent.Under the first embodiment, the baffles 470 have a lambda (λ) shapedprofile, such that the stem portion of a first lambda shaped baffle 470extends into a space beneath a second lambda shaped baffle 470, leavingenough space for smoke to traverse the vent, but blocking direct lightfrom entering the chamber 430 through the vent. The orientation of thelambda baffle stem pointing into the chamber 430 may facilitate ingressof smoke into the chamber 430.

As shown by FIG. 4, the inner surface of the ceiling 460 within thechamber 430 may preferably be treated to disperse and/or absorb lightwithin the chamber 430. For example, the surface may be textured orpatterned to disperse and/or absorb light. Similarly, the surface may becoated with a substance that disperses and/or absorbs light. The ceiling460 includes an emitter aperture and an adjacent emitter mount 422 (FIG.5) configured to receive an emitter 420. The emitter 420 emits light ofa wavelength chosen to illuminate smoke particles. The emitter 420 maybe, for example, a light emitting diode (LED). As shown in FIG. 5, theemitter 420 is mounted within the emitter mount 422 such that theemitter 420 is positioned to emit a light beam into the smoke chamber430 without having the emitter 420 itself physically intruding into thesmoke chamber 430. Similarly, the ceiling 460 includes a detectoraperture and an adjacent detector mount 412 configured to receive adetector 410. The detector 410 is mounted within the detector mount 412such that the detector 410 is configured to detect light within thesmoke chamber 430 without having the detector 410 itself physicallyintruding into the smoke chamber 430. The detector 410 may be, forexample, a photodiode.

As shown by FIG. 6, the emitter 420 emits one or more light beams in alight path 620 in front of an emitting end of the emitter 420. Thedetector 410 detects light within a detection region 610 in front of adetecting end of the detector 410. The emitter 420 and detector 410 areoriented at an angle α (FIG. 7) with respect to the ceiling 460 suchthat emitter 420 light path 620 intersects with the detection region 610of the detector 410. This area of intersection is called theinterference zone 630. Smoke within the interference zone 630 isilluminated by light from the emitter 420, so that illuminated smokeparticles within the interference zone 630 may scatter light to bedetected by the detector 410. Smoke may be declared to be present withinthe smoke chamber when the intensity of light detected by the detector410 meets and/or exceeds an illumination threshold.

By locating the emitter 420 and detector 410 in the ceiling 460, theinterference zone may be positioned within the chamber 430, so that theemitter 420 and detector 410 do not physically obstruct ingress of smokeinto the chamber 430 through vents between the baffles 470 (FIG. 5). Inalternative embodiments, the emitter 420 and detector 410 may partiallyprotrude through the ceiling 460 into the chamber 430. The emitter 420and the detector 410 are positioned so the light beam path of theemitter 420 does not project directly into the detector 410. As shown byFIG. 7, the emitter 420 is oriented at an angle α relative to thedetector 410, where the angle is generally mandated by fire safetystandards. The angle α may be, for example, approximately 135 degrees.However, there is no objection to other angles.

The emitter mount 422 may be shaped to receive a selected emitter 420and the detector mount 412 may be shaped to receive a selected detector410 such that the emitter 420 and detector 410 are located and orientedat the desired angle α to form an interference zone 630 (FIG. 6) of thedesired proportions and location within the chamber 430. The emittermount 422 and detector mount 412 may be substantially tube shaped bothto accommodate the shapes of the emitter 420 and detector 410 and toguide the emitter 420 and detector 410 into desired mounting positions.

Returning to FIG. 5, the detector 410 may include electrical detectorleads 415. The emitter 420 may include electrical emitter leads 425. Theelectrical leads 415, 425 may be electrically connected to the printedcircuit board the integrated smoke cell 400 is mounted to. The printedcircuit board electrically connects the integrated smoke cell 400 withother components in a smoke detector system 1000 (FIG. 10), describedbelow. The electrical leads 415, 425 may be configured to electricallyconnect to the printed circuit board, for example, as through-holeleads, or as surface mount leads. It is desirable that the electricalleads 415, 425 do not block ingress of smoke into the chamber 430. Tothis end a modified baffle 475 may be used in proximity to theelectrical leads 415, 425. The modified baffle 475 may secure theelectrical leads 415, 425 within holes, slots, or ridges in the modifiedbaffle 475. In alternative embodiments the electrical leads 415, 425 mayshare a single modified baffle 475, or be electrically connected toproduce a single pair of leads combining the leads for any number ofemitters 420 and detectors 410 to minimize obstruction of airflow intothe chamber 430.

The integral one-piece housing 490 includes the baffles 470, ceiling460, and apertures for receiving the emitter 420 and detector 410. Thehousing 490 may also include one or more guide features, such aspositioning pins 480. The guide features may be used to orient thehousing 490 in relation to a PCB the housing 490 is mounted upon. Thepositioning pins 480 may pass through apertures in the PCB, extendingthrough a far side of the PCB in relation to a near side of the PCBwhere the housing 490 is mounted. The housing 490 is formed as one pieceof material. The material may be, for example, plastic or metal. Aplastic smoke detector housing 490 may be formed by injection molding.It may be desirable for the housing to have a melting point above themelting point of solder, so the housing remains intact while components,for example, the emitter 420 and detector 410 are soldered to the PCB.For a plastic housing 490, a portion of the mounting pins extendingthrough and past the far side of the PCB may be melted to secure thehousing 490 to the PCB. In alternate embodiments, the guide features maybe formed as tabs or ridges that are secured by, for example, holes,troughs or ridges in the PCB. Similarly, other alternative embodimentsmay provide for the smoke cell 400 to be attached to a PCB using surfacemount device (SMD) techniques. For example, electrical leads 415 may bebent so that a portion of the leads are parallel to the plane of the PCBto allow them to lie flat onto the PCB and thereby be soldered using,for example, solder paste and reflow methods.

Second Embodiment

FIG. 8 shows a second exemplary embodiment of an integrated smoke cell800. The smoke cell 800 has an integral one piece housing 890 includinga ceiling 860 and side wall formed from a series of spaced baffles 870.The housing 890 is configured to be mounted to a PCB (not shown), suchthat the ceiling 860, side wall and PCB form a smoke chamber 830. Smokemay enter the chamber 830 through vents between the baffles 870. Theceiling 860 has apertures formed to permit chamber 830 access to one ormore emitters 820, and one or more detectors 810 mounted outside thechamber 830. The second embodiment as shown in FIG. 8 includes twoemitters 820, and two detectors 810. An emitter 820 and a detector 810may be paired, such that the emitter 820 is positioned substantiallydiametrically opposite across the ceiling 860 from the detector 810.Emitters 820 and detectors 810 are configured to be mounted in theceiling 860 so they either do not physically protrude into the chamber830, or so they only minimally physically protrude into the chamber 830,thereby not interfering or minimally interfering with the ingress ofsmoke into the chamber 830. The emitters 820 may be mounted in emittermounts 822, and the detectors 810 may be mounted in detector mounts 810,wherein the emitter mounts 822 and detector mounts 812 are integrallyformed with the ceiling 860.

The smoke detector 800 shown in FIG. 8 has two emitter-detector pairs.Each emitter-detector pair may be configured to emit and detect the samewavelength or range of wavelengths, or each emitter-detector pair may beconfigured to operate on different wavelengths or wavelength ranges. Afirst pair may be configured to emit and detect a first wavelengthselected to detect a first type of smoke, and a second pair may beconfigured to emit and detect a second wavelength selected to detect asecond type of smoke. For example, For example, the first pair may beoperate with a first wavelength to detect black smoke resulting fromburning materials, while the second pair may be operate with a secondwavelength to detect white smoke, which may result from frying food.Other pairs may be tuned to wavelengths for different purposes, forexample, to detect steam, chemical smoke, or dust particulates, or otherparticles.

The interference zones of each emitter-detector pair may be configuredto intersect, as shown in FIG. 8, or they may be configured to besubstantially independent, for example, if the emitter-detector pairsare configured in parallel alignment. A single emitter 820 may beconfigured to form an interference zone with two or more detectors 810.The single emitter 820 may produce light having one wavelength, twowavelengths, or a range of wavelengths. Similarly, a single detector 810may be configured to form an interference zone with two or more emitters820. A single detector 810 may be configured to detect a singlewavelength, multiple wavelengths, or a range of wavelengths. Alternativeembodiments may vary the number of emitters 820, the number of detectors810, and the ratio of the number of emitters 820 to detectors 810.Emitters 820, detectors 810, and emitter-detector pairs may beconfigured to operate concurrently or at separate times, for example,according to a duty cycle. In addition, other electronic components maybe housed within the integrated smoke cell, for example, an ASIC, andassembled on the plastic housing.

Method

FIG. 9 is a flowchart of an exemplary embodiment of a method formanufacturing an integrated smoke cell. It should be noted that anyprocess descriptions or blocks in flow charts should be understood asrepresenting modules, segments, portions of code, or steps that includeone or more instructions for implementing specific logical functions inthe process, and alternative implementations are included within thescope of the present invention in which functions may be executed out oforder from that shown or discussed, including substantially concurrentlyor in reverse order, depending on the functionality involved, as wouldbe understood by those reasonably skilled in the art of the presentinvention.

As shown by block 910, the method includes forming a ceiling portion ofan integral housing. A step includes forming a first component mountconfigured to receive and position a first component above a firstaperture formed in the ceiling, as shown by block 920. A step includesforming a second component mount configured to receive and position asecond component above a second aperture formed in the ceiling, as shownby block 930.

A smoke permeable wall having a series of baffles mounted around theperimeter of the ceiling is formed, as shown by block 940. The formingof the ceiling, wall and component mounts is preferably done byinjection molding of a material, for example, plastic, into a shapedmold. An emitter is installed into the first component mount, and adetector is installed into the second component mount, as shown by block950.

System

FIG. 10 is a schematic diagram of an exemplary smoke detector system1000 including an integrated smoke cell. The integrated smoke cell maybe the smoke cell 400 of the first embodiment having a single ceilingmounted emitter and a single ceiling mounted detector, or it may be thesmoke cell 800 (FIG. 8) of the second embodiment having multiple ceilingmounted emitters and/or detectors. The smoke cell detector provides asignal to a sensor circuit 1010. When smoke 1001 enters the smoke cell400, the sensor circuit 1010 determines the level of smoke 1001 presentin the smoke cell 400 based on the signal provided by the smoke celldetector to the sensor circuit 1010. The sensor circuit 1010 may includea logic circuit, for example, including a microprocessor and storage forinstructions for the microprocessor with threshold levels configuringthe sensor circuit to determine when smoke 1001 is present in the smokecell 400. Upon sensing smoke 1001, the sensor circuit 1010 provides atrigger signal to an alarm circuit 1020 that activates an alarmmechanism, for example a speaker/oscillator 1030, or a visual alertmechanism such as a strobe light (not shown). The components 400, 1010,1020, 1030 may be powered by a power supply 1040, for example, a wiredpower supply or a battery. Of course, this is just one example of asmoke detector system, and persons having ordinary skill in the art willreadily understand how the smoke cell 400 may be used in othervariations of smoke detector systems.

An integral one piece housing for a smoke cell may be advantageous overcomposite housings. For example, an integral housing may be more stable.An integral housing may simplify ensuring alignment between the emitterand detector, and alignment of the interference zone within the chamberthan housings formed of two or more pieces. Similarly, a one piecehousing may simplify the manufacturing process of mounting the housingto a PCB, thus reducing manufacturing cost, and facilitating, forexample, automated assembly on a smoke detector board and testing withinthe manufacturing process.

FIG. 11 is a schematic diagram of the integrated smoke cell in FIG. 6attached to a circuit board. The circuit board is labeled “CB.” All ofthe other reference numerals in FIG. 11 were discussed above withreference to FIG. 6.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.For example, in a third exemplary embodiment, a smoke cell may have afloor portion mounted upon a printed circuit board, where the integratedsmoke cell having a wall and ceiling are mounted upon the floor portion.The floor portion may be treated to absorb, disperse, and/or reflectlight in a desired manner. For example, it may be desirable for thefloor portion to absorb light from an emitter mounted in the ceiling ofthe integrated smoke cell. In view of the foregoing, it is intended thatthe present invention cover modifications and variations of thisinvention provided they fall within the scope of the following claimsand their equivalents.

What is claimed is:
 1. A method for manufacturing an integrated smokecell comprising: forming an integral housing comprising a ceilingportion comprising a first component mount disposed on an exteriorceiling side substantially above a first aperture in said ceiling, and asecond component mount disposed on said exterior ceiling sidesubstantially above a second aperture in said ceiling and a smokepermeable wall portion comprising a series of spaced baffles mountedsubstantially around a perimeter of an interior side of said ceiling;and mounting a circuit board to the integral housing so that theintegral housing and the circuit board collectively define a smokechamber that is bounded by the ceiling portion of the integral housing,the smoke permeable wall portion of the integral housing and the circuitboard, wherein said first component mount is configured to receive andposition a first component and said second component mount is configuredto receive and position a second component.
 2. The method of claim 1wherein said forming comprises injection molding a material into a mold.3. The method of claim 2, wherein said material comprises plastic. 4.The method of claim 1, further comprising: installing a first componentinto said first component mount; and installing a second component intosaid second component mount.
 5. The method of claim 4, wherein saidfirst component comprises an emitter and said second component comprisesa detector.
 6. The method of claim 1, wherein the emitter defines anemitting region in the smoke chamber adjacent to the emitter, whereinthe detector defines a detecting region in the smoke chamber adjacent tothe detector, wherein the detecting region at least partially intersectsthe emitting region in the smoke chamber, and wherein the emitter andthe detector are disposed substantially outside said smoke chamber. 7.The method of claim 1, wherein mounting the circuit board involvesapplication of one or more surface mount techniques.
 8. A methodcomprising: forming a housing having a ceiling portion and a smokepermeable wall portion, wherein the ceiling portion of the housing has afirst aperture and a second aperture, mounting a circuit board to thehousing so that the housing and the circuit board collectively define asmoke chamber that is bounded by the ceiling portion of the housing, thesmoke permeable wall portion of the housing and the circuit board;placing an emitter in the first aperture in the ceiling portion, whereinthe emitter defines an emitting region in the smoke chamber adjacent tothe emitter; placing a detector in the second aperture in the ceilingportion, wherein the detector defines a detecting region in the smokechamber adjacent to the detector.
 9. The method of claim 8, wherein thedetecting region at least partially intersects the emitting region inthe smoke chamber, and wherein the emitter and the detector are disposedsubstantially outside the smoke chamber.
 10. The method of claim 8,wherein the housing is configured to mount to the circuit board, and thecircuit board forms a floor of the smoke chamber, wherein the floor ofthe smoke chamber is opposite the ceiling portion of the smoke chamber,and wherein the detecting region at least partially intersects theemitting region between the floor of the smoke chamber and the ceilingportion of the smoke chamber.
 11. The method of claim 8, wherein thecircuit board is mounted to the housing using one or more surfacemounting techniques.
 12. The method of claim 8, wherein forming thesmoke permeable portion of the housing comprises forming a plurality ofbaffles disposed adjacent to the ceiling portion of the housing, whereinsaid baffles are arranged to allow ingress of smoke into the smokechamber and to obstruct ingress of light into the smoke chamber.
 13. Themethod of claim 12, further comprising: arranging the baffles in thesmoke permeable wall portion of the housing in a substantially circularpattern on a surface of the ceiling portion.
 14. The method of claim 13,wherein said emitter and said detector are mounted at diametricallyopposed positions across the substantially circular pattern.
 15. Themethod of claim 12, wherein each of said baffles has a substantiallychevron-shaped profile or a substantially lambda-shaped profile.
 16. Themethod of claim 12, further comprising: providing at least one of thebaffles with a guide feature configured to position the housing relativeto the circuit board.
 17. The method of claim 8, further comprising:treating an interior surface of the ceiling portion of the housing todisperse light.
 18. The method of claim 8, further comprising: disposingthe emitter at a first angle with respect to an exterior surface of theceiling portion; and disposing the detector at a second angle withrespect to the exterior surface of the ceiling portion.
 19. The methodof claim 18, wherein the first angle is substantially equal to thesecond angle.
 20. The method of claim 8, wherein: placing the emitter inthe first aperture in the ceiling portion comprises mounting the emitterin an emitter mount in the first aperture; and placing the detector inthe second aperture in the ceiling portion comprises mounting thedetector in a detector mount in the second aperture.
 21. The method ofclaim 8, further comprising: extending a first electrical lead from thedetector, through the housing, and to the circuit board; and extending asecond electrical lead from the emitter, through the housing, and to thecircuit board.
 22. The method of claim 21, wherein the smoke permeablewall portion of the housing has a modified baffle, relative to the otherbaffles, in proximity to the first electrical lead or the secondelectrical lead, wherein each modified baffle is configured to secure atleast one of the first electrical lead or the second electrical leadwithin a hole, slot, or ridge in the modified baffle to minimizeobstruction of airflow by the first electrical lead or the secondelectrical lead into the smoke chamber.
 23. The method of claim 8,wherein the housing is integrally formed.